In the fastening of thermal insulation materials to roof decks for roof assemblies of various buildings, one encounters a number of problems, whether the installation be a retrofit or new installation. Frequently mechanical fastener means or assemblies are used, such as screws with stress-distributing washers and the like. Where the screws are of metal or of a material readily conductive of cold or heat, even if the head of such screw be covered by a waterproofing membrane, exterior and environmental temperatures are conducted by the metallic screw along its length from head to tip. Where the screw tip has penetrated , such as by a self-tapping screw through a metal deck component, so that the screw's tip is exposed to the interior of a building, there have been encountered corrosion problems in the vicinity of metal deck penetration in that humidities within the building and a tip about as cold as the screw head has led to moisture condensation on the screw portion projecting interiorly in the building. In some instances, this moisture condensation has been so great that water drips from the exposed screw's tip. Where `plastic` fasteners are employed, heat and cold conduction problems and great temperature differences are avoidable, but in their installation it invariably is necessary to predrill a hole for the plastic fastener in roof decks of metal, wood, etc., which the plastic fastener can not readily penetrate. Another problem encountered with installed roof insulation material, and particularly in roof assemblies wherein an insulation material layer thereof be compressible, occurs, when, for example, a person walks thereon and is what is called fastener "pop". In such roof assemblies invariably the head of a fastening screw, e.g. a self-tapping screw, lies somewhere near the exterior surface of the roof assembly and the screw's tip is anchored in the roof deck (e.g. sheet metal). Upon pressure on the roof, such as a person's step on, or adjacent to, an installed screw, the roof's insulation yields and compresses, while the head of the screw does not yield, but instead the head "pops" or causes a rupture, or at least an upward dimple, in the roof's overlying waterproofing membrane or cover layer. Where the roof's insulation component be resilient and recovers to its original thickness upon removal of the pressure on the roof, the screw's head may again now be in its original position, but damage has occurred already of a leaky roof where waterproofing overcoating or membrane has been ruptured because of the screw's head "pop", or of a weakening of the overcoating membrane at the pop's dimpling location and with continued roof traffic resulting in a shortening of roof life in that dimpling stresses from fastener's head "pop" by successively encountered and eventually causes rupture and roof leaking.
The present invention advantageously overcomes and provides useful solutions to the just-mentioned problems and other problems encountered in roof assemblies. Additionally, other advantages are provided by the invention such as easy and rapid installation of roof assemblies involving insulation material overlying roof deck. One notable advantage of the invention is a providing of roof assemblies comprising a plurality of the invention's fastener assemblies, mechanically securing insulation material, and an installed overlying waterproofing membrane of so smooth an appearance as to make locations of the fastener assemblies visibly nondetectable by absence in the membrane of noticeable "imprint" or unevenness pinpointing fastener locations.